Q: Pre-oxygenation (or denitrogenation) is an important step during intubation. What length of time is good to perform pre-oxygenation to avoid rapid hypoxemia during intubation?



Answer: About 3 minutes


Nitrogen constitutes about 79% of air. Goal of pre-oxygenation is to replace nitrogen at the alveolar level causing nitrogen washout and creating an oxygen reservoir in the functional residual capacity of the lungs. Most of denitrogenation occurs in 2 minutes. Good preoxygenation of about 3 minutes may provide up to 8 minutes of apnea time in otherwise healthy adults but the desaturation rate is more rapid in sicker patients because of their higher metabolic rate and underlying pulmonary disease such as ARDS.

Various methods to provide good preoxygenation includes high-flow oxygen via a nonrebreather face mask (spontaneously breathing patient) or by using Ambu bag. 8 deep breaths over 60 seconds by using full vital capacity should provide good pre-oxygenation. Also BiPap mask is a good way of performing good denitrogenation. Patients on non-invasive mask ventilation should be left on it till intubation procedure is set to perform.

Q: Why Daptomycin is a bad choice for use in Pneumonia?


Answer: Daptomycin is a bad choice in the treatment of respiratory tract infections because surfactant in lungs binds daptomycin, leaving free drug concentrations in pulmonary secretions to very minimal. This is the only known organ-specific inhibition of an antibiotic.


Inhibition of daptomycin by pulmonary surfactant: in vitro modeling and clinical impact. - J Infect Dis. 2005 Jun 15;191(12):2149-52.